The fraudulent use of credit cards is becoming more prevalent every year. Credit card blanks are most commonly fabricated from plastic material and comprise a core sheet, usually polyvinyl chloride or copolymers thereof, upon which certain information concerning the issuer of the credit card is printed. The printed core may be overlayed with a vinyl film on one or both sides and the film is heat laminated to the core stock. Adhesives are commonly used to provide for firmer bonding of the core stock to the overlay. An example of such a laminated structure is set forth in U.S. Pat. No. 4,133,926.
It is also known to provide identification cards which have been specifically devised to be resistant to counterfeiting. One such structure comprises a laminate of a polyester film layer laminated to a uniaxially oriented plastic by means of an adhesive layer, as disclosed in U.S. Pat. No. 4,343,851. Other such identification cards are disclosed in U.S. Pat. No. 4,325,196.
As is well known, credit cards also contain embossed characters identifying the name and account number of the credit card holder. These characters are offset and raised such that the information may be transferred to charge slips. In conventional practice, printing is applied directly to the plastic core sheet, while embossing is effected after the core sheet has been laminated between the vinyl films.
Unfortunately, the embossed characters on lost or stolen credit cards made from the conventional thermoplastic materials can be easily altered. One or more of the embossed characters can be shaved off the surface of the card and a different character pasted on. Thus two digits of an account number can be transposed giving an entirely different number. Embossed names can be altered or shortened using the same technique.
Still another technique for altering credit card characters is to simply iron them out. Thermoplastic material can be made to flow by the application of pressure and sufficient heat thereby removing the embossed characters. New characters may then be embossed by simply stamping them at the appropriate location on the card.
If these and similar alteration techniques are done carefully enough, it may be very difficult to differentiate between an altered card and an original.
Accordingly, it is an object of this invention to provide a plastic credit card having embossed characters which can not readily be altered or removed.
Yet another object is to provide a plastic credit card which can not readily be re-embossed with altered characters.